Electric switch



P 1937. K. H. SOMMERMEYER 2,092,478

ELECTRIC SWITCH Filed March 2, 1936 3 Sheets-Sheet l p 7, 1937. K. H. SOMMERMEYER 2,092,478

ELECTRIC SWITCH Filed March 2, 1936 3 Sheets-Sheet 2 I I d4 m.

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P 7, 1937- K. H. SOMMERMEYER 2,092,478

ELECTRIC SWITCH Filed March 2, 1936 3 Sheets-Sheet 3 Patented Sept. 7, 1937 PATENT OFFICE ELECTRIC SWITCH Karl H. Sommenneyer, Evanston, Ill., asaignor to G-M L o ato fl, Inc., Chicago, 111., a corporation of Illinois Application March 2. 1936, Serial No. 66,547

13 Claims.

The present invention relates to electric switches and more particularly to the mechanical construction and operation thereof.

Electric switches are widely used for opening and closing power circuits in all types of electric apparatus. Generally speaking, the size and specific design of a. switch is determined by the load which it is required to control. Thus, a switch is limited as to the size of the load which it can control by the amount of current which it can carry in the closed condition and by the amount of power which it can dissipate in an are when it interrupts a circuit. The amount of current which a switch can carry is determined by the heat generated in the switch due to the resistance of the switch. The load whicha switch interrupts is measured roughly by the product of the closed circuit current and the open circuit voltage. The interrupting capacity of the switch is determined by the are which it can extinguish.

The tendency for an arc to form and to maintain itself after being formed increases both with the voltage and current of the circuit. Generally, the l'imit of the interrupting capacity of the switch is determined largely by the heating effect of the arc incident to the interruption of the circuit. If this are is permitted to persist for a considerable time it obviously will heat the contacts of the switch more than if it is extinguished promptly so that generally of two similar switches the one which extinguished the arc most quickly after the formation thereof will have the greater interrupting capacity. Arcs which form between the contacts of a switch as they open may be divided roughly into two general classes: Those that have the appearance of a spark and those that have the appearance of a flame. While every arc will not fall readily into one class or the other, the recognition of the two classes aids the study of arcs. The spark is the less severe of the two types. It usually has a blue color and is accompanied by a crackling sound. A telephone receiver or speaker connected to produce as sound, the variations of current or voltage vof the arc, will emit a crackling sound accompanied by a sharp thump. The flame persists for an appreciable interval of time. It gives off a bright colored 59 light such as red or yellow and is accompanied by a hiss or a roar both from the arc and the speaker. The thump from the speaker which indicates the final interruption of the current is comparatively weak in the case of the flame. An are which in appearance resembles both the spark and the flame will produce a frying noise in the speaker.

A load which produces only a spark at the contacts as the .gap opens, generally is well within the capacity of the switch, while one which 5 produces a pronounced or typical flame generally is near the limit of the capacity of the switch. The life of contact pieces depends to a considerable extent upon the load which the contacts handle, and generally the life is a continuous 10 function of load. Contact life depends largely on erosion. The erosion from a. spark generally is only oxidation. The oxide, if not volatile, is removed by the abrasive or cleaning action of the mechanical engagement of the two con- 15 tact pieces of the gap. A flame actually volatilizes some of the metal of the contact piece. Some of this metal enters the arc stream and thereby is transferred from one contact piece to the other. It is believed that this metal in the are 20 stll'eam aids the flame-like arc in sustaining itse f.

So long as the arc assumes a spark like character a set of contacts may appear to have an indefinitely long life running into millions of cy- 25 cles' of operation. But the same contacts sub- :Iected to a heavier load so that the arc assumes a decided flame like character may last only few hundred cycles of operation. And commercial acceptance tests of certain types of heavy duty 30 contactors have specified as few as five operations on a given overload.

It has been observed that the production of a flame-like are often marks a pronounced reduction in the life of a'set of contacts. Therefore it often happens that under certain conditions the life decreases at a greater rate or by a greater percentage than the load increases. The increase in load may consist of an increase in either the current or voltage of the circuit being inter- 40 rupted.

Under certain conditions a reductionof voltage will be more effective to reduce the tendency for the formation of a flame than a reduction in current. Or to put it differently, a reduction in voltage may permit the contact gap to control more power (product of current and voltage) without increasing the tendency for the formation of a flame. 50

The common methods of increasing the interrupting capacity of contacts may be summarized as follows:

1. Increasing the length of gap to which the switch contacts separate.

4. Reducing the voltage impressed across individual gaps by putting a number of gaps in series.

5. Making special provisions for preventing or opposing the formation of an arc and for extinguishing it if it does form, such as operating the switch in vacuum or oil, using magnetic blow outs and de-ionizing the gas in the arc.

The present invention is concerned with the perfection of the fourth of the above methods of increasing the arc interrupting capacity of electric switch contacts. It provides a mechanical system for operating a number of series connected contact gaps so that the load and the voltage properly divides between the several gaps.

In switches of the series connected gap type it is essential that all gaps should open at the same time. If one gap should open ahead of the others it may interrupt the circuit by itself and sustain the whole load. When this gap extinguishes its arc the circuit is broken and the other gaps opening subsequently have no work to perform.

If the one contact gap which opens first is unable by itself to interrupt the circuit, it is subjected to a severe flaming arc until one or more other gaps open to help it interrupt the circuit. opens first suffer the worst, the other contacts also suffer because when those other contacts do open the arc in the first gap, by heating the contact pieces and ionizing the air, will have lowered the resistance of that first gap to make it less effective as a circuit interrupt. It frequently is convenient to provide two contact gaps in a switch by the simple mechanical expedient of providing a movable piece of metal which is bridged across two stationary contact pieces. When the movable piece is lifted two contact gaps are established, one between the movable piece and each of the two separate stationary contact pieces. In a switch of this type it heretofore has been the common practice to provide a more or less fixed mechanical arm to operate the movable contact piece. In order to allow for non-uniformity of wear between the separate contact surfaces a resilient connection would be provided between the arm and movable contact piece. This resilient connection would. insure that the movable contact would engage both of the stationary contact pieces so as to close the circuit. However, when the contacts would open, one of the gaps generally would open ahead of the other and in so doing it would sustain the brunt of the work of opening the circuit. The arc, which occurred incident to the breaking of the circuit would burn the contact material and in the case of metals, would oxidize it. Where the metal was oxidized, the oxide generally would be worn oif rapidly by subsequent operations of the switch. It was inevitable, that the While the contacts of the gap which' 2. Increasing the speed at which the contacts greater wear, this faulty condition of early operation of one gap would grow worse as the switch was used until eventually one gapwould be doing all the work. The bad effects of uneven distribution of the load in switches heretofore known have not been confined to transferring the total wear to one set of contact pieces. It also has increased the total wear andreduced the capacity of the switch to that of the single contact gap which did all the work of breaking the circuit. Thus, for example, a switch having two contact gaps in series, for a certain type of service might be given a rating of 20 amperes 220 volts. When the switch operated correctly, each gap would control 20 amperes at 110 volts. If the switch should impose the whole load on one contact gap the rating might have to be reduced, for example, to amperes, 220 volts. In other words, the higher voltage per gap reduces the capacity of each gap and the reduced capacity of one gap becomes the total capacity of the whole switch.

It is a primary object of the present invention to provide an operating mechanism for a switch having a plurality of gaps in series which will insure that all gaps open simultaneously.

It is a further object of my present invention to provide a supporting and operating mechanism for a bridging contact piece which will automatically aline it with the stationary contact pieces with which it is to cooperate.

It is a further object of my invention to provide means in the operating mechanism of a switch having a number of contact gaps for automatically adjusting, compensating and cor-' recting for uneven wear of contact surfaces and misadjustment resulting from accident or mechanical wear.

It is a further object of the present invention to provide a mechanism for operating several contact gaps of a switch which the contacts open simultaneously regardless of large manufacturing tolerances, uneven wear of gontgact pieces and/or misadjustment of the con- In order better to acquaint those skilled in the art with the teachings and practice of the will insure that present invention, I now shall describe certain specific embodiments thereof, references being made to the accompanying drawings in which:

Figs. 1 and 2 are a plan and elevation respectively of a relay embodying my present invention.

Fig. 3 is a partial section taken along the line 3-3 of Fig. 1.

Fig. 4 is a partial'section similar to Fig. 3 but showing the mechanism in a different operated position.

Fig. 5 is a section taken along the line 55 of Fig. 2.

Figs. 6 and 7 are diagrams for illustrating the operation of the apparatus of my present invention.

Figs. 8 and 9 area plan and elevation respectively of another relay having a switch construction embodying my present invention.

'Fig. 10 is an enlarged detail section of a part of the contact mechanism of the relay of Figs. 8 and 9, Fig. 10, being taken along the line l0l0 of Fig. 8 and looking in the direction of the arrows.

Fig. 11 is a section taken along the line ll-l| of Fig. 10 and looking in the direction of the arrows.

Figs. 12 and 13 are plan. and elevational views of still another relay having. a switch construction embodying my present invention.

Fig. 14 is an enlarged detail section of a part of the switchmechanism of the relay of Figs. 12 and 13, taken along the line |3- |3 of Fig. 12.

Figs. 15 and 16 are a sectional elevation and a plan respectively of still another switch construction embodying my present invention.

. armature l2.

The switch contacts comprise a pair of stationary contact pieces 2| and 22 and a bridging contact piece 23. The bridging contact piece 23 is secured by means of a insulator 24 which in turn is riveted to an eye in one end of the bar 25, a clearance hole being provided in the contact 23 for the rivet which secures the insulator 24 to the bar 25. As is best shown in the sectional view of Fig. 3, the bar 25 extends through a slot 21 in a bracket 28 which is carried by the The other end of the bar 25 is bent at a right angle at 23 and fits loosely into a hole 33 extending through the bracket 25 and the armature piece l2. A flat strip spring 32 fits closely over the end 23 of the bar 25 so asto prevent it from slipping cut of the hole 30; and the end of the spring 32 bears against the rod 25 so that the spring 32 and the bracket 23 firmly grip the rod 25. Except for the grip and force of the spring 32, the bar 25 is free to move in the slot 21 of the bracket 23 and to hinge inthe hole 35. Furthermore, the looseness of the fit of the bent end of the bar 25 in the hole 33 permits the bar 25 to rotate, that is, to twist in the grip of the spring 32. The grip of the spring 32 resists this rotation by the friction of the grip. The spring 32 exhibits substantially no resilience in the direction of rotation of the rod 25 and therefore it exerts no force tending to rotate the rod 25 or to restore it to any rotated position. This characteristic 'of operation results from the fact that the force or restraint of friction is non conservative in that it dissipates and does not conserve to the mechanical system the energy expended in working against it. A resilient restraint, on the other hand, is conservative in that it conserves the energy and returns it later in the form of a restorative eifort. The grip of the spring 32 resists but does not produce rotation of the bar 25. Therefore it tends to hold the bar 25 in any position in which it happens to stop- The armature I2 is adapted to be attracted by the magnet so as to move the bridging contact 23 into engagement with the two stationary contact pieces 2| and 22. When the magnet II is de-energized, a spring 34 restores the relay substantially to the condition shown in Fig. 2.

When the armature I2 is attracted by the magnet II it rotates about the bearing provided by the blind rivets ll thereof which engage 'the iron frame I3 as shown in Fig. 2.v In so doing, it first brings the bridging contact 23 into simultaneous engagement with the two stationary contact pieces 2| and 22. In so doing it may cause the contact piece 23 to operate in approximately the manner illustrated diagrammatically in Fig.

' 6. Inasmuch as the bar 25 is capable of rotating in the bracket 28, the bridging contact 23 may assume any random position such as the position in which it is shown in solid lines in Fig. 6. As the bar 25 moves it towards thecontact pieces 2| and 22, it reaches the position 23A shown in dotted lines in which it engages only the contact piece 2|. In this condition it cannot close the circuit controlled by the switch because it does not complete an electrical path between the two stationary contact pieces 2| and 22. Continued motion of the bar 25 causes the bridging contact 23 to rotate into the position 233 also shown in dotted lines in which it engages both the contact pieces 2| and 22 so as to complete the electrical connection between those stationary contact pieces. During the motion Just described, the bar 25 has twisted or rotated in the grip of the spring 32 and the bracket 23, but it has not moved in the slot 21. Further motion of the armature l2 towards the magnet coil I causes the bar 25 to move in the slot 21 because the bracket 23 is carried by the armature |2 into the position shown in Fig. 4. whereas the bar 25 isprevented from moving therewith due to the engagement of the bridging contact 23 with the stationary contact pieces 2| and 22. This flexes the spring 32, and the force of the spring is borne by the contact pieces 2| and 22. The

force of the spring 32 therefore provides the contact pressure.

when the bracket 25 continues to move with the armature l2 after the bridging contact 23 has come into engagement with both of the contact' pieces 2| and 22 so that the bar 25 moves in the slot 21, the contact piece 25 is forced to slide slightly across the contact surfaces of the contact pieces 2| and 22 so as to provide a slight scouring action. This occurs as follows:

The armature l2, when it operates, rotates about its point of fastening indicated approximately by the reference numeral in Fig. 3 where the blind rivets l4 engage the iron frame II. It is also to be observed that the rod 25 articulates with respect to the armature l2 at its,end 29 where it engages the hole 30. After the bridging contact 23 has engaged the two stationary contact pieces 2| and 22, the armature |2 continues to rotate in a counter clockwise direction as viewed in Fig. 3 so that the point 23 continues to describe an are about the point 35. In so doing, the point 29 moves towards the left as viewed in Figs. 3 and 4, and therefore forces the bar 25 and the contact piece 23 also to move towards the left as viewed in Figs. 3 and 4, and in so doing to wipe the contacting surface of the bridging contact 23 against the contacting surfaces of the stationary contact pieces 3| and 32.

The contact piece 23, as it rotates from the position shown in solid lines to the position 233 in Fig. 6, turns in the grip of the spring 32. Inasmuch as the spring 32 exerts only a frictional restraint upon the rotation of the rod 25 in its grip, it shows no tendency whatsoever to rotate the rod 25 so as to bring the contact piece 23 back towards the position 23A. Consequently, when the magnet releases the armature l2, the rod 25 will draw the bridging contact piece 23 away from the stationary contact pieces 2| and 22 without producing any rotation whatsoever of the bridging contact 23. This is illustrated diagrammatically in Fig. 7 where the contact piece 23 is indicated as being moved from the position shown therein in solid lines to the position 230 shown in dotted lines without any rotation thereof whatsoever. If the bar 25 contact pieces 2| and 22, this will be immaterial because it will take place before the contact piece 23 disengages the stationary contact pieces 2| and 22. As long as the spring 32 continues to exert contact pressure the bridging contact 23 will engage both of the contact pieces 2| and 22. When the bracket 28 again comes into engagement with the rod 25 and thereby removes the pressure from the contact surfaces of the-several contact pieces 2|, 22 and 23, the contact piece 23 begins to move away from the two stationary contact pieces. As it does so, it is held in the grip of the spring 32 and the bracket 28 and it is frictionally restrained from rotating. Consequently, it disengages the two stationary contact pieces 2| and 22 simultaneously.

Because the spring 32 can exertno forc'etending to rotate the rod 25, it must of necessity withdraw the bridging contact 23 from the stationary contact pieces 2| and 22 without rotation. Therefore, it cannot open one contact gap ahead of the other. Since the spring 32 exerts some frictional restraint at all times upon the bar 25 to prevent rotation thereof, the bridging contact 23 tion of the switch so as to insure that bothgaps will open simultaneously when the switch is required to interrupt the circuit. This characteristic of operation of the switch is obtained by supporting the mechanism of the switch so as to permit it to rotate and so as to impose a frictional restraint, and also eliminate any resilient loosely in a hole 46 in the bracket 42 and armature 4|, all of which is similar to the construction illustrated in Figs. 1 to 4 inclusive. The round bar 44 has welded thereto at its outer end, a cross bar 48 which lies substantially at a. right angle to the bar 44. The opposite ends of the rod 48 carry round insulators 49 and 50 which in turn carry bridging contacts. 5| and'52. The bridging contact 5| is adapted to engage stationary contact pieces 55 and 56, and the bridging contact piece 52 is adapted to engage stationary contact pieces 51 and 58. The construc-* tion of the bridging contact 52 is more clearly illustrated in the enlarged sectional detail views of Figs. 10 and 11. As shown in Figs. 10 and 11, the bridging contact 52 comprises a pair of formed conducting pieces 6| and 62 which fit loosely into a circumferential groove in the insulator 50 and which are riveted together so as to be held thereby on the insulator 50. The insulator 50 fits tightly onto the rod 48 so as to be nonrotatable thereon.

The conducting pieces 6| and 62 which constitute a part of the bridging contact 52 fit loosely onto the insulator 56 so as to permit the bridging contact 52 to rotate thereon. A spring orv resilthe conducting piece 6|.

restrains rotation of the bridging contact 52 about the insulator 59.

A pin 54 in the insulator 50 is adapted to engage the edges of a notch in the arcuate center portion of the piece 6| so as to limit the rotation of the bridging contact 52 about its insulator 50. A similar pin 53 limits the rotation of the bridging contact 5| aboutits insulator 49. These pins 53 and 54 'may be omitted if desired because in general no harm can result from the bridging contact accidentally being brought into engagement with only one of its stationary contact pieces (assuming that the switch is open). However, it is important .that' the bar 44 be limited in its rotation in order that one of the bridging engagementywith both its stationary contact This grip frictionally pieces. A twopole'fswi't'ch usually is so wiredas j to. interrupt bothsides of a 'tWoIWire-line andthereby to isolate the load completely fromthe" thereby would be connected to one side-of the line. Such a situation could constitutea hazard. Rotation of the bar is limited by'thebent end '45 of the rod 44 engaging sides of the hole" 46 in the bracket 42 and armature 4|"in which the bent over end 45 of the rod 44 is inserted. 1

The relay of Figs. 8 and 9 is adaptedto be connected to control both wires of a two wire line so that when the switch is open both sides of the line are completely disconnected from the load. Thus one side of the line may be 'con-' g nected to each of the stationary contact-"pieces. 55 and 51 and the load may be connected to the the spring 43 to be substantially equally distributed among the four contact gaps, and compels those four contact gaps to open simultaneously. Thus, the friction grip of the bridging contact 52 on the insulator 50 causes the bridging contact 52 to disengage the stationary contacts '51 and 58 simultaneously and, similarly, the frictional engagement of the bridging contact piece 5| with the insulator 49 causes the bridging contact 5| to disengage the stationary contact pieces 55 and 56 simultaneously. The frictionally restrained rotation of the bar 44 under the spring 43 causes the two bridging contacts 5| and 52 to leave their respective pairs of stationary contacts simultaneously.

contact gap of the switch in excess of one contact gap requires a separate adjustment or degree of freedom in order that the operating mechanism automatically may align the contacting pieces so as to open all contact gaps simultaneously.

- s The switch of Figs. 1 and-2 has two contact v gaps and therefore employs. a mechanism proient member 64 gripped between the pieces 6| viding. one adjustment, or one degree of freedom 165. It may be stated as the general rule that each in adjustment. This single adjustment or single degree of'freedom is provided by the rod 26 which is rotatable in its support. The switch of Figs. 8 and 9 which has four contact gaps employs mechanical connections providing three separate adjustments, or adjustments providing three degrees of freedom. These three adjustments or degrees of freedom are provided by the three separate mechanisms or mechanical connections already described andenumerated.

Figs. 12 and 13 illustrate a switch mechanism having one mechanical connection which in itself provides two degrees of freedom of adjustment.

In Figs. 12 and 13 an armature II of the relay carries an arm I2 which is secured resiliently to the armature I I. As isshown more clearly in the sectional detail of Fig. 14, the arm 12 is perforated at its outer end to receive a pin I3. Pin I3 carries a contact disk I6 which is formed at its center to fit a spherical head I6 of the pin 13. The pin I3 extends through a large clearance hole in the contact disk I5 and also through a collar 11 which has a curved surface which also fits the curvature of the formed center portion of the contact disk I5. A coil spring I9, which bears against a washer 60 secured to the pin 13 by a cotter pin I5 or the like, causes the spherical head 16 and the collar 'I'I to firmly grip the formed center portion of the contact plate 16. The plate I5 is permitted to slide in the grip of the head I6 and collar 11. This gives the contact plate I6 two degrees of freedom of adjustment and permits it to align itself with three stationary contact pieces. The plate or disc 15 has two degrees of freedom of adjustment because it is free to rotate independently about two different axes of rotation for adjusting the relative order of opening of the contact gaps.

As is illustrated in Figures 12 and 1 3, the contact plate I5 is adapted to engage three stationary contact pieces ill, 62 and 63 when the armature II is in its normal or released position, and to engage three other stationary contact pieces 6|, 65" and 66 when the armature II is in its drawn up position. It is immaterial that the contact plate 16 may have to adjust itself to a slightly different position for engaging each of these two sets of three stationary contacts. It will automatically align itself with each set of contacts as it engages the same and then will act to disengage all three of those stationary contact pieces simultaneously.

If itis desired, the clearance hole in the formed central portion of the disc I6 may be made small tolimit the motion and range of adjustment of the plate 15. However, since the contact disc 16 of the relay of Figures 8 and 9 engages stationary contacts in both the normal and released posi-' tions of the relay, the disc I5 is not subject to accidental misalignment, and it should not be necessary to limit its range of adjustment. If either one of the two sets of stationary contacts should be omitted, then it might be desirable to limit the range of adjustment of the disc I6.

The contact disc 15 preferably is made round as shown so that it may rotate about the axis of the pin I3 without affecting its operation or its ability to engage the several stationary contact pieces. The switch of Figures 12 and 13 may be employed for opening a three phase star connected circuit. Thus each of the three branches of the load may be connected between a separate conductor of the three phase line and a separate one of the three stationary contacts of the group 64, 65, 86. While the three contact gaps of such an arrangement will not be in a single series circuit, each gap will be separately in series with.

the other two. Therefore, if one gap fails to open it imposes an additional load on each of the others. The switch of Figs. 12 and 13 also may be employed for controlling two load circuits which are to be disconnected from each other when tie-energized. Thus one side of a two wire line may be connected to the stationary contact piece 04 and one side of each load may be connected to a separate one of the two stationary contact pieces 66 and 66. The other sides of the loads may be connected to the other side of the line. The gap at the contact piece 64 then will be in series separately with each of the gaps at the contact pieces 66 and 66.

In Figs. 15 and 16 I have illustrated a contact mechanism providing five degrees of freedom for operating simultaneously six contact gaps. Therein, an operating arm 9| is provided with a spherically formed portion 92 which is gripped by concave and convex collars 93 and 94 under the pressure of a spring 95,- all of which is carried on a rod 96 which passes through a clearance hole in the center of the formed portion 92. This construction is similar to the mounting of the contact disc I5 of Figs. 12, 13 and 14 and provides two degrees of freedom of adjustment. The arm 9I may be resiliently secured to an armature of a relay magnet in the same manner as is the arm I2 of Figs. 8 and 9. The rod 96 is bent at 91 and at its end 90 carries an insulator 99 which in turn carries a bridging contact piece I which is adapted to rotate on the insulator 98 but is frictionally restrained from doing so. The bridging contact I00 and its insulator 99 are of a construction similar to that of the bridging contact 52 and its insulator 50 illustrated in Figs. 10 and 11. Welded to the rod 96 is another rod I02 carrying insulators I03 and I04 at opposite ends thereof. The insulators I03 and I04 in turn carry bridging contacts I and I06 which are similar to the bridging contact I00. These three bridging contacts I00, I05 and I06 are adapted to engage six stationary contacts shown in Fig. 16 and: numbered I0'l to H2 inclusive. 'I'hisprovides six contact gaps which, because of the five degrees of freedom of adjustment provided in the operating mechanism, are controlled to open their gaps simultaneously.

A pair of stops or guides 69 and 90 depend from the arm 9I on opposite sides of the end 96 of the rod 96. This prevents rotation of the whole contact assembly about that portion of the rod 96 which carries the collars 93 and 94 and thereby keeps the several bridging contacts I00, I06 and I06 in positions to engage their respective stationary contact pieces. As in the case of the switch of Figs. 8 and 9, the clearance hole in the formed portion 92 of the arm 9| may be made small to limit the range of the adjustment provided thereby.

While I have shown and described certain speciflc embodiments of my present invention, it will be apparent to those skilled in the art that the same are by way of illustration only. Therefore, I do not wish to be limited except by the scope of the appended claims.

I claim:

1. In combination, contact pieces adapted to provide a plurality of contact gaps, a single actu ator for the contact pieces of all said contact gaps,

said actuator being adaptedto hold all said gaps open simultaneously and being adapted also to hold all said gaps closed simultaneously, said actuator including adjustable" mechanical connections interconnecting the contact pieces of all said gaps to provide a contact pressure equalizing system such that a change of contact pressure in any one gap can'produce a change of pressure in all other contact gaps, and means for restrain! in said mechanical connections to oppose the equalization of'contact pressures, the restraining forces being substantially non-restorative.

2. In combination, contact pieces adapted to provide a plurality of contact gaps, a single actuator for the contact pieces of all said contact gaps, said actuator being adapted to hold all said gaps closed simultaneously, said actuator including mechanical connections interconnecting said contact pieces, said connections being adjustable as respects the relative order of closing said contact gaps to the extent of a number of degrees of freedom which number is one less than the number of said contact gaps, and means for imposing restraints onall said adjustments, said restraints involving only forces which are substantially non-restorative.

3. In combination, contact pieces adapted to provide a plurality of contact gaps, a single actuator for the contact pieces of all said contact gaps for closing all said gaps, said actuator including mechanical connections interconnecting said contact pieces, said connections being adjustable as respects the relative order of closing said contact gaps to the extentof a number of degrees of freedom which number is one less than the number of said contact gaps, and means for imposing non-restorative restraints on all said adjustments.

4. In combination, a pair of contact pieces, a bridge contact adapted to lie in simultaneous engagement with both-said contact pieces, first means for moving said bridge contact into and out of engagement with said contact pieces, mounting means for mounting said bridge contact on said first means so as to cause said bridge contact to be carried by said first means but permitting said bridge contact to orient itself with respect to said contact pieces to alter the order in which it engages said separate contact pieces, said mounting means'including means for imposing a restraint upon thev orientation of said bridge contact piece, said restraint consisting solely of forces which are non-restorative.

5. In combination, a pair of contact pieces, a bridge contact adapted to lie insimultaneous engagement with both said contact pieces, first means for moving said bridge contact into and out of engagement with said contact pieces, mounting means for mounting said bridge contact on said first means so as to cause said bridge contact to be carried by said first means but permitting said bridge contact to orient itself with respect to said contact pieces to alter the order in which said bridge contact engages said sepa-- rate contact pieces, said mounting means including means for imposing a restraint upon the orientation of said bridge contact, said restraint consisting solely of forces which are nonrestorative, said mounting means including also a member carrying said bridge contact which is rotatable with respect to said first means.

6. In combination, a pair of contact pieces, a bridge contact adapted to lie simultaneously in engagement with both contact pieces of said pair, first means for moving said bridge contact into and out of engagement with said contact pieces, mounting means for mounting said bridge contact on said first means so as to cause said bridge contact to be carried by said first means but permitting said bridge contact to orient itself with respect to said contact pieces to alter the order in which said bridge contact engages said separate contact pieces, said mounting means including means for imposing a frictional and substantialLv non-resilient restraint upon the orientation 9! said bridging contact piece.

7. In combination, abridge contact, means for mounting said bridge contact so as topermit it to rotate about an axis, a pair of separate contact pieces adapted to engage and bear against said bridge contact, so that the separate pressures of said separate contact pieces tend to re:- tate said bridge contact in opposite directions about said axis, and means imposing a non-re-' storative restraint upon the rotation of said bridge contact about said axis.

8. In combination, contact pieces adapted to provide two contact gaps, a single actuator for the contact pieces of bothsaid gaps, said actuator being adapted to hold both of said gaps open simultaneously, adjustable mechanical connections between the actuator and the separate contact pieces for permitting one of said gaps to be lengthened by shortening the other while said actuator is stationary, said connections including means for imposing a frictional restraint upon the lengthening and shortening of said contact gaps as aforesaid, said actuator and said connections also including means for imposing a force of such magnitude on each contact piece as to provide a contact pressure at each of-said gaps in excess of the pressure that would be required at that gap for overcoming said frictional restraint in the absence of any pressure at the other gap.

9. In combination, contact pieces adapted to provide two contact gaps, a single actuator for said contact pieces, said actuator being adapted to holdboth of said contact gaps open simultaneously, adjustable mechanical connections between said actuator and the contact pieces of said gaps, said connections being adJustable to alter the order in which said contact gaps close, said connections including means for imposing a non-restorative restraint upon the adjustment of the order of operation of said gaps, said nonrestorative restraint being adapted to provide forces of such magnitude as to produce separately at each gap a component of contact pressure in excess of any component of pressure produced at said gap by any restorative force which acts to restrain the alteration of said order of operation of said contact gaps.

10. In combination, a switch base, an actuator movable with respect to said base and having a slot on a movable portion thereof, the long iiimension of said slot lying in a direction which is less than 90 degrees from the direction of motionof said movable portion, a round rod having a first portion thereof engaging said slot, said rod being rotatable in said slot, said rod also being movable in said slot laterally with respect to itself and longitudinally with respect to said slot, said actuator including means for limitingthe motion of said rod towards one end of saidslot, a spring engaging said rod and urging it towards said one end of said slot, said spring being inef-' fective to rotate said rod aboutthe axis of said rod, a bridging contact carried by said'rod at a second portion thereof, said bridging contact having contacting portions located on opposite sides of a first plane containing the axis of said rod, two stationary contact pieces on said base each of which has a contacting portion adapted to be engaged by a separate one of said contacting portions of said bridging contact, said stationary contact pieces having their contacting portions on opposite sides of a second plane containing the axis of said rod and making an angle of less than 90 degrees with that component of the direction of motion of said movable portion of said actuator which is perpendicular to the axis of said rod, said stationary contacts also having their contacting portions on the same side of a third plane containing the axis of said rod and making an angle of 90 degrees with the second plane.

11. In combination, contact mechanism providing a plurality of contact gaps, said mechanism including stationary contact pieces and a movable member which is required to be aligned with said stationary contact pieces, an actuator member movable with respect to said stationary contact pieces, a mechanical connection between said actuator member and said movable member for mounting said movable member on said actuator member to be carried thereby, said connection comprising means on one of said members for resiliently gripping the other, said other member being movable in the grip thereof to orient the movable member with respect to said stationary contact pieces, said means being substantially ineffective resiliently to restrain the movement of said other member in said grip, whereby said other member is frictionally and substantially non-restoratively restrained from moving with respect to said one of said members, and

' electric circuit connections connecting said contact gaps in series with each other in an electric circuit.

12. In combination, contact mechanism providing a plurality of contact gaps, said mechanism including stationary contact pieces and a movable member which is required to be aligned with said stationary contact pieces, an actuator member movable with respect to said stationary contact pieces, a mechanical connection between said actuator member and said movable member for mounting said movable member on said actuator member to be carried thereby, said connection comprising spherically concave and convex gripping pieces and a spring on one of said members, the other member having a spherically curved portion gripped by said gripping pieces, said other member being movable in the grip of said gripping pieces, said gripping pieces and spring being substantially ineffective resiliently to restrain movement of said other member in said grip, whereby said other member is capable of rotating with'respect to said first member independently about two different axes but is frictionally and substantially non-restoratively restrained from so rotating, and electric circuit connections connecting said contact gaps in series with each other in an electric circuit.

13. In combination, contact mechanism providing a plurality of'contact gaps, said mechanism including stationary contact pieces and a movable member which is required to be aligned with said stationary contact pieces, an actuator member movable with respect to said stationary contact pieces, a mechanical connection between said actuator member and said movable member for mounting said movable member on said actuator member to be carried thereby, said connection comprising means on one of said members for resiliently gripping the other, said other member having a cylindrical portion gripped by said means, said cylindrical portion being rotatable in the grip of said means to orient the movable member with respect to said stationary contact pieces, said means beingsubstantially ineffective resiliently to restrain rotation of said other member in said grip, whereby said other member is frictionally and substantially nonrestoratively restrained from rotating with respect to said one of said members, and electric circuit connections connecting said contact gaps in series with each other in an electric circuit.

KARL H. SOMIERMEYER. 

